This invention relates, in general, to remotely controlled valves of the type which may be employed in hydraulic control systems and, in particular, this invention relates to a shut-off valve used to control high-pressure hydraulic fluid.
A shut-off valve may be employed in a hydraulic control system for selectively blocking the flow of hydraulic fluid through the system in one mode of operation and for passing the flow of hydraulic fluid in a second mode of operation. Hence, the shut-off valve is basically a hydraulic on-off switch. For example, in combination with a large steam turbine, a steam inlet valve controls the steam inflow into the turbine. The steam inlet valve may be hydraulically positioned against a valve closing spring by means of a hydraulic cylinder which receives an input of hydraulic fluid from a hydraulic manifold which includes a servo-valve which controls the flow of hydraulic fluid to the cylinder. The input flow to the hydraulic manifold is controlled by a shut-off valve. If the shut-off valve fails in an open position, the hydraulic fluid would be uselessly pumped to drain. If the shut-off valve fails in a closed position, the steam inlet valve cannot be hydraulically controlled. This foregoing example is illustrated in U.S. Pat. No. 3,495,501 to Kure-Jensen issued Feb. 17, 1970. In that patent, a shut-off valve 5 controls the inflow of pressurized fluid to servo-valve 6 which, in turn, controls the fluid supply for positioning a steam valve 1. The shut-off valve, itself, is hydraulically and remotely positioned by a trip valve 13.
Prior art valves used in the aforementioned environment have been known to malfunction due to jamming, rusting, plugging and leaking. In the prior art, a spool type of valve has been employed wherein jamming could occur if contaminates become wedged between the spool and the housing bore. One source of contamination could be rusting especially when water and moisture has found its way into the pressurized hydraulic fluid. Leakage is objectionable in a shut-off valve for obvious reasons and also because it requires an increased pump capacity to maintain the desired hydraulic pressure and hence presents an increase in turbine losses and a decrease in turbine efficiency. Rusting can also cause plugging of hydraulic lines by dispersing rust contaminates throughout the hydraulic system.
The present invention improves the prior art shut-off valves in the following manner. A valve housing includes an inlet port and an outlt port with a valve seat therebetween. The valve seat is part of an axial bore formed through the valve housing. A valve member is slidable within the axial bore and includes a hemispherical poppet which is self-aligning with respect to the valve seat. The valve member also includes a spool at each end which defines a diametrical clearance between the spool circumference and the bore circumference. Each spool also includes a slide means which bears against the interior of the axial bore so that the valve member floats within the axial bore, and the slide means in combination with the spool clearance can wipe contaminates from the bore surface. The foregoing arrangement increases the efficiency of the hemispherical poppet and seat seal, while also obviating any tendency of the valve member to jam or stick. Moreover, because of the inherent simplicity of construction the valve may be formed from a stainless steel material to obviate rusting without any additional internal sleeving and surface treatments.
It is therefore one object of the present invention to provide an improved shut-off valve wherein the potential for jamming is greatly reduced.
It is another object of the present invention to provide a shut-off valve wherein the sealing arrangement between the inlet and outlet ports is improved.
These and other objects and advantages of the present invention will become apparent from the following detailed description of the invention when taken in connection with the appended drawing.